The fine structure of young and old spinal ganglia.

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T H E FINE STRUCTURE O F YOUNG AND OLD
SPINAL GANGLIA
ARTHUR HESS2
Department of Anatomy, Washington University School
of Medicine, S t . Louis, Missouri
SEVENTEEN FIGURES
Despite the intensive studies devoted to the structure of
nerve cell bodies and the extracellular and intracellular elements associated with them, there are still many aspects of
the structural organization of the cells of the spinal ganglia
awaiting final resolution.
It has been suggested that there are various nerve cell
types in spinal ganglia, and some authors have even assigned
different functional properties to these cells based on a histological study of sections with the light microscope (see Bacsich
and Kyburn, '53). The disposition of the Nissl bodies, mitochondria, and Golgi apparatus in these cells has occupied
much attention (Beams, van Breemen, Newfang and Evans,
'52). The satellite cells of the ganglion also have been investigated. I n addition, the ageing of nerve cells and the accumulation of lipofuchsin pigment (Andrew, ' 5 2 ) has been observed frequently.
I n this study of spinal ganglia, we have attempted, through
the application of ultrathin sectioning and electron mieroscopy to:
(1) ascertain the possible occurrence of cell types and
charactekize morphologically the basis for any such cell variants ;
'This investigation was supported in part by research grants B-341 and
R-425 from the Institute of Xeurdogical Diseases and Blindness of the National
Tnstitutes of Health, Public Health Service.
2With the technical assistance of Charles E. Houck, Jr. and Emil C. Sanders.
399
400
ARTHUR HESS
(2) study the fine structure of the karyoplasm, nucleolus,
and cytoplasm or neuroplasm;
( 3 ) resolve further the structure of Nissl bodies or chromophil substance ;
(4) determine the disposition and structure of mitochondria ;
(5) study the occurrence and structure of the Golgi apparatus ;
(6) study the morphology of the satellite cells and their
relationship to the spinal ganglion nerve cells and to each
other ;
(7) investigate in senile animals the spinal ganglion cells,
their mitochondria and the distribution and fine structure
of the pigment and to draw some conclusions as to the probable mechanism of its formation.
MATERIAL AND METHODS
The spinal ganglia of guinea pigs were used. The animals
were divided roughly into three groups : (1)youw.9 animals
of three days of age; (2) aduEt animals that had given birth
to at least one litter; ( 3 ) old or senile animals of 6 years of
age. These latter animals were donated generously by Dr.
James B. Rogers of the Department of Anatomy, University
of Louisville School of Medicine, Louisville, Kentucky, to
whom we are very grateful.
The techniques were essentially the same as those used
previously for the study of the fine structure of peripheral
nerve fibers (Hess and Lansing, '53). The spinal ganglia,
dissected most frequently from thoracic vertebral levels, were
placed in Dalton's fixative (Dalton and Felix, '55) for onehalf to two hours. Most of the sections examined were obtained from material allowed to fix for one and one-half
hours. The ganglia then were washed in distilled water and
placed in 70% alcohol, dehydrated and embedded in a mixture of partially polymerized butyl arid methyl methacrylate.
A few ganglia were also fixed in buffered osmic acid ( Palade,
'52a), varying in concentration from 17. to 3% and contain-
FINE STRUCTURE OF SPINAL GANGLIA
401
ing mammalian Ringer’s solution, for 4 hours, then similarly
treated as above. The fixation yielded by Dalton’s fluid was
vastly superior. Previous studies in this laboratory have
shown that nerve tissue has a predilection to swell and
“explode” during the embedding process. The use of partially polymerized plastic for embedding usually prevents
this, although it does not invariably yield perfect results.
Sections were made and mounted on copper mesh grids,
which were then inserted into an RCA-EMU type microscope.
Negatives were exposed at a magnification of 1000 to 6000 X
and photographically enlarged.
To facilitate identification of the cellular elements and to
determine the location in the ganglia of the section under
observation in the electron microscope, thin plastic sections
were studied in the phase-contrast microscope. Reference
was also made to cytological and neurohistological frozeii
and paraan preparations of spinal ganglia to correlate observations made with the light and electron microscopes.
RESULTS
Spinal garzg1io.n Nerve cells
Cell types. I n ganglia from guinea pigs of all ages, two
distinct cell types are found (fig. 1). I n one, the cells are
small, the cytoplasm is very osmophilic, and the ground substance or iieuroplasm of the cell is well organized; the chromophil substance extends evenly throughout the cell (fig. 15).
In the other cell type, the cells are large, the intensity of
osmophilia is low, the Nissl substance is easily recognized
and organized into scattered clumps or bodies (fig. 7). That
this is a real difference and is not necessarily a factor induced by fixation can be seen by observing these two cell
variants in juxtaposition to one another. The main difference between these two cell types resides in the distribution
of the Nissl substance, with the first or “dark” type of cell
having chromophil substance extending throughout the length
and breadth of the cell, thus giving high electron density to
402
ARTRUR HESS
the cytoplasm; while the second or “light” type of cell has
Nissl substance distributed in discrete clumps and producing
in general a low electron density of the cytoplasm.
There are transitional cell types with density of cytoplasm
and of cytoplasmic elements ranging in intensity between
the “dark” and “light” cell variants (fig. 1). However, the
“dark” and “light” cell types as indicated above are representative of such a dichotomy in spinal ganglion nerve cells.
The remaining items will be discussed in relation to the
cell types, and the differences, if any, in the morphology or
disposition of the elements under consideration will be noted.
Nucleus and wucleolus. The nucleoplasm of spinal ganglion
cells is sparse and irregularly dispersed (fig. 16). The nucleus
possesses a typical double membrane (figs. 15 and 16). The
nucleolus is very dense and consists of at least three components (fig. 16). One is a vesicular component with filaments
enclosing small vacuoles and is the most prominent part of
the nucleolus. Another portion of the nucleolus, most frequently intimately associated with the filamentous structure,
is a dense irregular mass yielding mainly a homogeneous
appearance with only a few large granules. Other irregular
masses, presenting a more granular appearance than the
former and less dense, comprise the third component of the
nucleolus.
Any one of these three nucleolar components can be found
adherent or closer to the nuclear membrane than the others
(fig. 9), yielding an appearance similar to that of the nucleolar satellite (Barr, Bertram and Lindsay, ’50) ; we have no
information as to its significance.
There are no differences in the cell types of nucleus or
nucleolus. The nucleolar satellite body also appears in both
cell types.
Cell membrane. The limiting cell membrane of the spinal
ganglion nerve cell presents a structure similar to the membranes of other cells. It is rather difficult to define its exact
structure and dimensions since the satellite cell, to be discussed later, is in juxtaposition with it.
FINE STRUCTURE O F SPINAL GANGLIA
403
Most frequently, the nerve cell membrane is smooth. However, often it reveals thin villiform projections extending
outward from the nerve cell surface (fig. 7). The margins
of these processes are continuous with the cell membrane.
The less dense central portion of these projections has the
same density as the nerve cell cytoplasm, so that these villiform projections are true processes of the nerve cell. The
projections are also seen cut in cross-section. They are
probably due to the harsh treatment accorded the nerve cell
by fixation.
Neurofibrils. We have seen no structure in the cytoplasm
that can be interpreted as a neurofibril. Indeed, the opposite
view is probably true in that there appears to be no orientation in the cytoplasm, either of the neuroplasm itself or of
the distribution of the cytoplasmic elements, except for the
internal organization of the Nissl substance discussed below.
The fibrillar structures mentioned by Beams et al. (’52) as
neurofibrils do not appear in our material.
Chromophil substance. The observation that Nissl bodies
contain ribonucleoprotein suggests that this substance should
appear morphologically similar to the structural system described as “endoplasmic reticulum” by Palade and Porter
(’54)’ “erga~toplasm’~by Weiss (’53), and double-niembraned system by Weiss and Lansing ( ’53). Although none
of these terms is entirely appropriate for nerve tissue, the
term “ergastoplasm” will be used in this paper. The latter
presumably corresponnds to the basophilic material in cytoplasm (Bernhard, Haguenau, Gautier and Oberling, ’52).
Haguenau and Bernhard ( ’53) have described Nissl material
in nerve cells with the use of the electron microscope.
When the Nissl substance is viewed under relatively low
magnification, it appears as a densely-packed mass of small
granules (figs. 7 and 15). However, with higher magnification, some of the granules can be resolved as very fine
tubular filaments surrounded by granules (figs. 11 and 14).
This is an appearance similar to endoplasmic reticulum or
ergastoplasm previously described in nerve tissue (Hess and
404
ARTHUR HESS
Lansing, ’ 5 3 ) . The tubular filaments are in layers, one placed
on top of the other. The granules are perhaps more numerous
than those of ergastoplasm in other cells. At higher magnifications, the granules are seen t o have smaller, denser
granules in and around them, yielding a punctate appearance. I n addition, the granules associated with the tubular
filaments are usually not only aligned against the filaments,
but also frequently can be found evenly-spaced in a row between the filaments. The tubular elements of each Nissl body
are also highly oriented, so that in a mass of Nissl, all the
components are sectioned in the same direction. One Nissl
body may have its tubules cut neatly in cross-section; while
in an adjacent clump of Nissl, all the units niay be cut tangentially.
Clumps of Nissl substance appear only in “light” cells;
aggregations occur throughout the cytoplasm of “dark” cells.
However, even though the distribution of chromophil substance differs in the two cell types, the units composing the
Nissl substance are the same (figs. 11 and 14).
Mitochondria. The mitochondria are small, thin, and elongated and possess the cristae or folds characteristic of this
organelle (figs. 7, 11 and 15). They are, in principle, similar
to mitochondria previously described (Palade, ’52b ; Hess and
Lansing, ’53). Higher magnifications reveal at times that
the folds of mitochondria do not pass across the entire width
of the mitochondrion, but are seen cut in cross-section (fig.
12). The haphazard arrangement of the folds in the interior
of the mitochondrion indicate that perhaps the main folds
possess villous extensions. Y-shaped and T-shaped bifurcating mitochondria have also been noticed.
One is impressed by the relatively small diameter of several of the mitochondria in these nerve cells. As an approximation, several of them are as little as one-half the diameter
of the mitochondria in many tissue cells. Another point
worthy of note is the close packing and large number of mitochondrial folds. While this is by no means diagnostic for
FINE STRUCTURE O F SPINAL GANGLIA
405
nerve cells, it is unlike the situation in the mitochondria thus
f a r described in most other tissues. The density of intramitochondria1 matrix material even within a single cell is
variable from one mitochondrion t o the next. The mitochondria are also considerably shorter than those found in axons
(Hcss and Lansing, ’ 5 3 ) .
S o difference exists between the mitochondria in different
cc.11 types. The structure of this organelle will again receive
attention when discussing ageing in nerve cells.
Golgi upparatus. I n preparations studied with the light
microscope, the Golgi apparatus, revealed by appropriate
silver and osmic acid techniques, is well developed in spinal
ganglion cells. A structure, similar to that described by
Sjostrand and Hanzon (’54) and Dalton and Felix (’55) in
electron micrographs as the Golgi apparatus, is found in
sections of spinal ganglion cells studied with the electron
microscope. This material is located easily and extensively
throughout the cytoplasm of spinal ganglion cells (figs. 7,
11, and 15). It occurs near the nucleus (fig. 15) as well as
near the cell membrane (figs. 7 and 11),which illustrates its
extensive disposition.
Its morphology is similar t o the structure called the Golgi
apparatus and described in other cells by Sjorstrand and
Hanzon ( ’54) and Dalton and Felix ( ’55). The material consists of membranes, granules, and vacuoles (fig. 12). The
membranes are similar in size to ergastoplasmic filaments.
The granules, however, are clear in the center and surrounded
by a more dense border, in contrast t o the punctate appearance of ergastoplasmic granules. The vacuoles are the outstanding component of this structure. They are encased by
the membranes and are apparently clear in the center. The
size of the vacuoles appears to differ in various cells. However, this difference has not been correlated with the “dark’’
or “light’, cell types or with the location of the Golgi complex near the nucleus or near the cell membrane.
406
ARTHUR HESS
Satellite cells
Nucleus. The nucleoplasm of the satellite cell usually presents a more or less homogeneous appearance with the dense
chromatin material dispersed throughout the nucleus (fig.
17). At times, the chromatin material is not so evenly dispersed and is aggregated into several irregular clumps (fig.
8). The nucleoplasm is much more dense than that of the
nerve cell.
The satellite cell nucleus is usually intimately related to
the nerve cell. It is either separated from the nerve cell by
its own intervening cytoplasm or rests on the nerve cell,
giving the appearance of a demilune. Frequently, the satellite
cell nucleus has a more intimate relation to the nerve cell and
causes an indentation in the cytoplasm of the nerve cell (fig. 5).
Cytoplasm. The cytoplasm of the satellite cell is very difficult to fix. It frequently tears away from the nerve cell.
At times, it appears relatively devoid of formed elements.
However, favorable preparations reveal that the cytoplasm
is fairly dense, containing scattered ergastoplasmic filaments
and granules and mitochondria that compare in size with those
of the nerve cell (fig. 8).
The satellite cell cytoplasm completely surrounds the nerve
cell, even though at times it appears thin and attenuated
(figs. 11 and 15).
Cell mernbrame. The limiting membrane of the satellite cell
presents the structure typical of other cells (figs. 8, 11, and
15). The cell membrane of these cells can be divided into
two parts - that apposed t o the ganglion nerve cell and the
surface distal to the nerve cell. Both surfaces are usually
relatively smooth, the former following the contour of the
ganglion cell and the latter, the surface of satellite cells belonging to neighboring nerve cells or the outlines of an intervening connective tissue capsule (figs. 11 and 15).
However, a frequent occurrence, usually near the nucleus
of the satellite cell, is the appearance of a collection of membranes (figs. 13 and 17). These membranes, each of about
PINE STRUCTURE O F S P I N A L GANGLIA
407
the same thickness as the limiting membrane of the satellite
cell elsewhere, twist and fold, establishing a complex labyrinthine apparatus. There are at least two relationships of
satellite cells that could account for this appearance. One
is that the varied membrane appearance is due to extensive
overlapping of processes of satellite cells belonging to one
nerve cell and serving to form its capsule. The other view
is that the complex apparatus represents local meanderings
of the membranes themselves of one satellite cell. Although
not definitely established, we at present tend to favor the
latter viewpoint. Evidence f o r this is that it is possible in
some sections to trace some of the membranous folds back
to the surface membrane of the satellite cell. It can then
be seen that both surfaces of the satellite cell membrane,
that apposed to the nerve cell and that distal from it, contribute to the complex membranous apparatus. Another point
in favor of this view is that the complex membranous apparatus occurs frequently near the nucleus of a satellite cell.
Since the nucleus of the satellite cell is located centrally in
the light microscope with approximately equal amounts of
cytoplasm extending from it, the location of the complex
membranous apparatus near the nucleus would indicate that
it is formed locally by the membranes of one cell. Of course,
it is not impossible that the overlap of cytoplasm of the
satellite cells belonging t o a single neuron is so extensive that
processes of satellite cells can extend for long distances
and reach as far as the centrally-located nucleus of an
adjacent satellite cell belonging to the same neuron, yielding
the folded membrane appearance.
The various relationships and appearances of the satellite
cell do not appear to be restricted to a single nerve cell type,
but can usually be found in relation to “dark” or “light”
cells.
There are similarities between satellite cells, Schwann cells,
and neuroglia. The similarities in the relationships of perineuronal glial satellites and nerve cells of the central nervous
system (see Penfield, ’32) and the satellite cells and spinal
408
ARTHUR HESS
ganglion nerve cells described here are striking. The nucleus
and the cytoplasmic contents of the satellite cells are similar
to those of Schwann cells (Hess and Lansing, ’53). The indentation of the cytoplasm of the spinal ganglion cell caused by
the satellite cell nucleus is reminiscent of the indenting of the
axon and myelin sheath by the Schwann cell nucleus (Hess
and Lansing, ’53). Since the neurilemma includes the membrane of the Schwann cell (Hess, ’55) and is a continuous
sheath throughout the extent of the peripheral nerve fiber, the
Schwann cell of adjacent internodal segments can be considered as forming a syncitium across the node of Ranvier,
even though the Scliwann cell cytoplasm might appear arrested at the node. Satellite cell cytoplasm surrounds the
spinal ganglion nerve cell. Among histologists, the prevailing view is that the satellite cells are continuous with
the neurilemma at the region of exit of the nerve process
and that the satellite and Schwann cells have a common origin
from the neural crest (see Singer, ’54). Thus the spinal
ganglion cell and its process that enters the peripheral nerve
(its dendrite) are enclosed in a continuous sheath of cells.
Rio-Hortega also believed in the similarities of neuroglia,
satellite cells, and Schwann cells and called the latter two
“peripheral neuroglia” (see Penfield, ’32).
Senile spinal garzglion rzcrue cells
Degeneration of cells, of course, may be found in senile
ganglia and these wi11 manifest hyperchromatic nuclei, chromatolysis, etc. (see Andrew, ’52). I n cells that are not in
the process of degeneration, the cell membrane, nuclear
nienibrane, nucleoli, and Nissl substance do not exhibit obvious
age changes. The accumulation of pigment, however, is a
characteristic of all senile spinal ganglion nerve cells. I n
addition, it is also necessary to comment on the structure
of the mitochondria since these organelles have been described
as undergoing profound alterations in structure with age
(Payne, ’52; Weiss and Lansing, ’53).
F I N E STRUCTURE O F S P I N A L G A N G L I A
409
Mitochondria. Characteristic mitochondria, as found in
nerve tissue (Hess and Lansing, ' 5 3 ) , are found in spinal
ganglion nerve cells with and without obvious age changes.
Thus, apparently intact mitochondria are found in ganglion
cells containing dense accumulations of pigment (fig. 4).
The mitochondria, exhibiting normal folds, are scattered at
random throughout the cytoplasm. However, we have also
observed swollen and vacuolated mitochondria in senile spinal
ganglion cells (fig. 3). These mitochondria conform closely
to the description of Weiss and Lansing ( '53) in their paper
on the age changes of the anterior pituitary of the mouse.
The mitochondria are several times enlarged and rounded ;
the matrix material is essentially lacking or very dilute as
evidenced by lack of density within the mitochondria. The
folds are barely recognizable as very short inward extensions
from the limiting membrane or surface of the mitochondria.
It is interesting to note that both the apparently intact
mitochondria and the degenerative mitochondria are found
in cells that appear well-fixed. This gives rise to the implication that at least some ganglion cells exhibit mitochondria1
ageing (Payne, '52; Weiss and Lansing, '53). However, we
have found comparable degenerative mitochondria in sections
of very young (three-day-old) and adult spinal ganglion
cells of guinea pigs in which pigment was absent and no age
changes had occurred (fig. 13). Since degenerative mitochondria can be found in young and adult cells and normal
mitochondria are seen in senile cells, it is difficult, at least
for individual spinal ganglion cells, to use the condition of
the mitochondria as an index of ageing.
Pigment. I n the extremely senile guinea pigs we have
studied, virtually all of the ganglion cells, despite cell type,
contain pigment bodies in varying amounts (figs. 4 and 6).
The pigment usually tends to form aggregations toward the
periphery and more frequently occurs around the entire
border of the cell, rather than in its interior.
The pigment bodies are characterized by very marked
electron density and vary in shape from spheroidal to highly
410
ARTHUR HESS
irregular bodies. Their density approximates that of lipoidal
inclusions or nucleolar material. Although the most frequent
appearance is that of a homogeneous mass, there are not uncommon exceptions. The pigment bodies are usually dense
and solid (figs. 4 and 10). However, in some instances, the
pigment body seems to be composed of a number of vesicles
of very low electron density surrounded by a lacework of
dense material (fig. 6). In still other instances, the combination of the aforementioned forms occurs with the pigment
body being composed of both solid and vesiculated forms
(fig. 6). Vesicles can vary from one to many in a pigment
body.
Beginning pigment formation seems to occur in most intimate relation with swollen mitochondria (figs. 2 and 10).
This relation of mitochondria and pigment is seen not only
in senile cells (fig. a),but also in adult animals (fig. 10) where
only infrequent cells exhibit small amounts of pigment. The
mitochondria swell, their borders become very dense, and
the internal folds disappear with the interior of the mitochondria assuming a homogeneous, less dense appearance. The
pigment granules accumulate in relation to the mitochondria
and extend from one pole of the mitochondria. Payne (’52)
has observed that one of the first changes in ageing mitochondria is that “they appear as brown pigment-like bodies.”
The accumulation of pigment apparently progresses by the
formation of a successive series of vesicles which then coalesce
to form a pigment body. A suggested series of stages in the
formation of a pigment body is presented in figures 2, 6 and 4.
SUMMARY
Ultrathin sections were made of the spinal ganglia of threeday-old, adult, and 6-year-old guinea pigs and examined with
the electron microscope. Two nerve cell types are observed,
mainly based on the distribution of the Nissl substance. The
nucleoplasm and three components of the nucleolus of the
neurons are described. The cell membrane of the nerve
cell can be smooth or can present thin villiform projections
F I N E STRUCTURE O F SPINAL GANGLIA
411
containing nerve cytoplasm. No evidence of neurofibrils is
seen. Nissl substance is composed of layers of fine tubular
filaments with granules apposed to them and lined up between
them, similar to the appearance of ergastoplasm in other
cells. The tubular elements of a Nissl bodyare oriented in
one direction. The mitochondria are usually small, thin,
and elongated and present numerous, closely-spaced folds.
The main folds might present villous extensions. A structure
similar to the Golgi apparatus of other cells occurs extensively
throughout the cell and can be found near the nucleus and
near the limiting cell membrane. It consists of membranes,
granules, and vacuoles and is similar to that described in other
cells.
The nucleus of the satellite cell is described. It can cause
an indentation in the nerve cell cytoplasm. The satellite
cell cytoplasm contains mitochondria and scattered ergastoplasmic filaments and granules. It encapsulates the neurons.
The membrane of the satellite cell is described. A complex
membranous apparatus, produced either by invagination and
folding of the membrane of a single satellite cell or by
overlapping of the processes of adjacent satellite cells, has
been found, usually located near the satellite cell nucleus.
A discussion is presented concerning the significance of
and comparing morphological similarities of satellite cells,
Schwann cells, and neuroglia.
Degenerative mitochondria can be found in young and
adult nerve cells and normal mitochondria are seen in senile
cells. It is difficult t o use the condition of the mitochondria as
an index of ageing. All senile ganglion nerve cells present
pigment. The appearance and distribution of the pigment
bodies are described. A suggested series of stages of pigment
formation, arising from swollen mitochondria, is presented.
LITERATURE CITED
ANDREW,W.
1952 Cellular Changes With Age. Springfield, Illinois; Charles
Thomas. 74 pp.
BACSICH,P., AND G. M. WYBURN 1953 Formalin-sensitive cells i n spinal
ganglia. Quart. Journ. Mier. Sei., 94: 89-92.
412
ARTHUR HESS
BARR,.M. L., L. F. BERTRAM
AND H. A. LINDSAY1950 The morphology of
the nerve cell nucleus, according to sex. Anat. Rec., 107: 283-298.
BEAMS,H. W., V. L. VAN BREEMEN,D. M. NEWFANGAND T. C. EVANS1952
A correlated study on spinal ganglion cells and associated nerve
fibers with the light and electron microscopes. J. Comp. Neur., 96:
249-281.
BERNHABD,
W., F. HAGUENAU,
A. GAUTIERAND C. OBERLIN 1952 L a structure
submicroscopique des elements basophiles cytoplasmiques dans le foie,
le pancreas et les glandes salivaires. Z. Zellforschg. mikr. Anat., 97:
281-300.
DALTON,A. J., AND M. D. FELIX1955 A study of the Golgi substance and
ergastoplasm in a series of mammalian cell types. Exp. Cell Res.
I n press.
F., AND W. BERNHARD
HAGUENAU,
1953 Aspect de la substance de Wissl au
microscope Blectronique. Exp. Cell Res., 4 : 4 9 6 4 9 8 .
HESS,A. 1955 The fine structure and morphological organization of non-myelinated nerve fibres. Proo. Roy. Soc. B. (in press).
HESS, A., AND A. I. LANSING 1953 The fine structure of peripheral nerve
fibers. Anat. Rec., 217: 175-200.
PALADE,
G. E. 1952a A study of fixation for electron microscopy. J. Exp. Med.,
95: 285-298.
195213 The fine structure of mitochondria. Anat. Rec., 114:
427451.
1954 Studies on the endoplasmic reticulum.
PALADE,
G. E., AND K. R. PORTER
I. I t s indentification in cells in situ. J. Exp. Med., 100: 641-656.
PAPNE,
F. 1952 Cytological changes in the cells of the pituitary, thyroids,
adrenals and sex glands of ageing fowl, p. 381-402. I n Cowdry's
Problems of Ageing, Third Edition, edited by A. I. Lansing. Williams
and Wilkins Co. : Baltimore.
PENFIELD,
W. 1932 Neuroglia. Normal and Pathological. I n Cytology and
Cellular Pathology of the Nervous System, VOI. 11, p. 421-479. New
York: Paul B. Hoeber, Inc.
SINGER,
M. 1954 Nervous system, p. 194-272. In Histology, edited by R. 0.
Greep. New York: Blakiston Co., Inc.
SJOSTRAND,
F. S., AND V. HANZON 1954 Ultrastructure of Golgi apparatus of
exocrine cells of mouse pancreas. Exp. Cell Res., 7: 415-429.
WEISS, J. M. 1953 The ergastoplasm. J. Exp. Med., 98: 607-618.
WEISS, J., AND A. I. LANSING 1953 Age changes in the fine structure of
anterior pituitary of the mouse. Pror. Soc. Exp. Biol. and M d . ,
8 2 : 460-466.
PLATES
PLATE 1
EXPLANATION OF FIGURES
All illustrations are electron micrographs of the spinal ganglia of guinea pigs.
All magnifications are approximate, The photographs of this plate are from
ganglia fixed i n Palade's ( '52a) fluid.
1 Spinal ganglion nerve cells illustrating the nerve cell types with varying
densities of cytoplasm. x 1000.
2
Apparently swollen mitochondrion (M) i n intimate relation with the
supposed beginning of pigment (P) formation. x 12000.
3
A neuron of a senile guinea pig showing swollen degenerative mitochondria
(M) and pigment (P). x 12,000.
4 A neuron of a senile guinea pig illustrating solid and dense pigment
bodies (P) and ixtact mitochondria (M). x 12,000,
5. A nerve cell and satellite cell nucleus showing the latter causing an indentation in the neuron cytoplasm. x 3000.
6
Seuron cytoplasm of a senile guinea pig showing vesiculated bodies ( P )
believed to be various stages in the formation of the pigment. x 12000.
PLATE 1
FINE STRUCTURE O F S P I N A L GANGLIA
ARTHUR RESS
415
PLATE 2
EXPLANATION OF FIGURES
All illustrations are electron micrographs of the spinal ganglia of guinea
pigs. All magnifications a r e approximate. The photographs of this plate a r e
from ganglia fixed i n Dalton’s (Dalton and Felix, ’55) fluid.
7
A “ l i g h t ” ganglion cell with clumped Nissl substance and villiform processes
extending from the cell membrane. The Golgi apparatus ( G ) is seen near
the cell membrane. A mitochondrion ( M) is also shown. X 15000.
8
A satellite cell nucleus with clumped chromatin. The satellite cell cytop1:isni
contailis mitochondria and scattered ergastoplasmic filaments and granules.
The satellite ecll limiting membrane can also be seen. X 15000.
9
P a r t of the nucleolus near the nuclear membrane of the nerve cell yielding
the appearance of a nucleolar satellite. x 15000.
10 A n adult nerve cell showing beginning pigment (P) formation cxtending
from the pole of swollen mitochondria ( M) . x 15000.
416
F I N E STRUCTURE O F S P l N A L G A N G L I A
PLATE 2
ARTHUR HESS
-
417
-
PLATE 3
EXPLANATION OF FIGURES
All illustrations are electron micrographs of the spinal ganglia of guinea pigs.
All magnifications are approximate. The photographs of this plate a r e from
ganglia fixed in Dalton’s (Dalton and Felix, ’ 5 5 ) fluid.
11 An illustration of the cytoplasmic contents of the “ d a r k ” cell type showi~ig
the similarity of the Nissl substance t o ergastoplasm ( E ) , ergastoplasmic
filaments and punctatc granules apposed t o and lined in a row between
the filaments, the Golgi apparatus (G) near the limiting meiiibrane and
mitochondria ( M ) . The thin satellite cell cytoplasm (SC) encapsulates tlie
neuron. The satellite cell limiting membraiie is also shown. X 24000.
12
A n enlargmient of figure 11 showing the Golgi apparatus with Golgi
vacuoles (Gv), membranes (Gm), and granules ( G g ) . The villous folds
of a mitochondrion (M) are also shown. X 42000.
418
PLATE 3
F I N E STRUCTLTRE O F S P I N A L GANGLIA
IRTHUR HESS
419
PLATE 4
EXPLANATION O F FIGURES
All illustrations are electron micrographs of the spinal ganglia of guinea pigs.
All magnifications are approximate. The photographs of this plate are from
ganglia fixed in Dalton’s (Dalton and Felix, ’55) fluid.
13
The complex nienibraiious apparatus ( M A ) of the satellite cell cytoplasm
is showii. The adult nerve cell has some swollen degenerative mitochondria
( M ) . X 15000.
14 A Nissl body of a “light” cell is shown and is similar t o ergastoplasm
with layers of fiIamerits and granules between them. X 20000.
420
PLATE 4
F I N E STRUCTURE OF SPiXAL GANQLIA
ARTHUR HESS
42 1
PLSTE 5
EXPLnNATION O F FI G U R E S
All illustrations are electron micrographs of the spinal gaiiglia of guinea pigs.
All magnifications are approximate. The photographs of this plate are from
ganglia fixed in Dalton’s (Dalton arid Felix, ’ 5 5 ) fluid.
15 Cytoplasm of a “ d a r k ” cell showing the diffuse and scattered Nissl
substance, Golgi apparatus (0) near the nerve cell nucleus (MN), and
mitochondria. ( M ) . The double-walled structure of the nerve cell nuclear
membrane is shown. The satellite cell cytoplasm ( S C ) encapsulates the
neuron. The satellite cell limiting nienibrane can also be sccn. x 20000.
16 A nerve cell nucleus showing the vesicular p a r t of the nucleolus (Nl), the
irregular homogenous mass commonly associated with it (N>), and the
other irregular pnnctate masses ( N 3 ) . The membrane of the nerve cell
nucleus is also shown. X 12000.
17
The complex membranous apparatus (MA) of the satellite cell cytoplasm
is shown near the satellite cell nucleus (SN). The satellite rcll nucleus is
more or less homogeneous i n appearance. X 15000.
423
PLATE 5
FINE STRLCTURE O F SPINAL GASGL1.1
ARTHUR HESS
423